Cancers of the biliary tract provide a unique opportunity to combine biochemistry and epidemiology to shed light on the possible etiology of cancers which are uncommon in the U.S. but of considerable international importance. Different parts of the biliary tract are bathed in the same material, bile. Yet, there are significant differences in the epidemiology of cancers of these different parts of the biliary tract. In addition, there are marked differences in the incidence of these diseases across countries. These findings have led to many hypotheses about etiology, including biochemical hypotheses arising out of preliminary work by the investigators: marked differences have been demonstrated in the bile and gallstone constituents of normal, cholelithiasis, and cancer patients in Bolivia and the U.S. In order to further investigate the risk factors and etiology of biliary tract cancers, a case-control study is proposed. Subjects will be collected from two collaborating Latin American centers: La Paz, Bolivia and Mexico City, Mexico. Three case groups will be recruited into the study, patients undergoing abdominal surgery who have newly-diagnosed: 1) cancer of the gallbladder, 2) cancer of the extra-hepatic biliary tract, and 3) cancer of the ampulla of Vater. Each case will be compared to two sets of controls: 1) abdominal surgery patients with cholelithiasis, and 2) abdominal surgery patients who have no biliary tract disease. Personal interviews will be used to obtain: demographic characteristics, prior medical history, family history, and exposure to agents presumed to be risk factors for biliary cancer. Bile, blood, and, where appropriate, gallstone specimens will be obtained from cases and controls during surgery and analyzed for various biochemical parameters. Univariate analysis, including calculation of odds ratios with confidence intervals, will be followed by stratification and multiple logistic regression, enabling us to evaluate the importance of each variable while adjusting for the others as confounders, as well as the relative importance of each variable as a risk factor.